Discrete active seal assemblies

ABSTRACT

Active seal assemblies employing active materials that can be controlled and remotely changed to alter the seal effectiveness, wherein the active seal assemblies actively change modulus properties such as stiffness, shape orientation, and the like. In this manner, in seal applications such as a vehicle door application, door opening and closing efforts can be minimized yet seal effectiveness can be maximized.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional Application of U.S. applicationSer. No. 11/074,575 filed Mar. 8, 2005 and relates to and claimspriority to U.S. Provisional Application No. 60/552,781 entitled,“Active Seal Assemblies” filed on Mar. 12, 2004, the disclosure of whichis incorporated by reference herein in its entirety.

BACKGROUND

This disclosure relates to seals and more particularly, to discreteactive seal assemblies for sealing opposing surfaces.

Current methods and assemblies for sealing opposing surfaces such asdoors and trunk lids, for example, include the use of flexible elasticmembranes and structures that compress upon pressing into the opposingsurfaces to close the gap between surfaces. Typical materials includevarious forms of elastomers, e.g., foams and solids, that are formedinto structures having solid and/or hollow cross sectional structures.The geometries of the cross sections are varied and may range fromcircular forms to irregular forms having multiple cavities, channels,slots and/or extending vanes.

Sealing assemblies are typically utilized for sound, airflow, and/orfluid management. The seals generally are exposed to a variety ofconditions. For example, for vehicle applications, door seals generallyare exposed to a wide range of environmental conditions such as rain,snow, sun, humidity and temperature conditions, and the like. Currentmaterials utilized for automotive seals are passive. That is, other thaninnate changes in modulus of the seal material due to aging andenvironmental stimuli, the stiffness and cross sectional geometries ofthe seal assemblies cannot be remotely changed or controlled on demand.

A problem with current seals is the tradeoff in seal effectiveness. Sealeffectiveness can generally be increased by increasing the interfacepressure and/or contact area of the seal. However, in sealingapplications, such as in vehicle doors, the increased interface pressureand/or contact area by non-active seals results in increased dooropening and closing efforts.

Accordingly, it is desirable to have active seal assemblies that can becontrolled and remotely changed to alter the seal effectiveness, whereinthe active seal assemblies change stiffness properties on demand, forexample, by changing the material's elastic modulus, or geometry, forexample by actively changing the cross-sectional shape of the seal. Inthis manner, in seal applications such as the vehicle door applicationnoted above, door opening and closing efforts can be minimized yet sealeffectiveness can be maximized.

BRIEF SUMMARY

Disclosed herein are active seal assemblies. In one embodiment, theactive seal assembly comprises a seal body formed of an elastic materialintegrated with a seal base; a wire and/or strip partially embeddedwithin the seal body having an end that exits the seal body, wherein thepartially embedded wire and/or strip is positioned within the seal bodysuch that a shape of the seal body changes in response to a forceexerted on the wire and/or strip; an active material in operativecommunication with the end of the wire and/or strip, wherein the activematerial is effective to undergo a change in at least one attribute inresponse to an activation signal, wherein the change in the at least oneattribute exerts the force on the wire and/or strip; an activationdevice in operative communication with the active material adapted toprovide the activation signal; and a controller in operativecommunication with the activation device.

In another embodiment, the active seal assembly comprises a seal bodyformed of an elastic material integrated with a seal base, wherein theseal body comprises a hollow interior channel; a wire or strip disposedwithin the hollow interior channel comprising a plurality of stiffelements directly attached to the seal body and the wire or strip; anactive material in operative communication with the end of the wire orstrip, wherein the active material is effective to undergo a change inat least one attribute in response to an activation signal, wherein thechange in the at least one attribute exerts a force on the wire or stripsuch that a shape of the seal body changes in response to a forceexerted on the wire or strip; an activation device in operativecommunication with the active material adapted to provide the activationsignal; and a controller in operative communication with the activationdevice.

In yet another embodiment, the active seal assembly comprises a sealbody formed of an elastic material integrated with a seal base, whereinthe seal body comprises a hollow interior channel; a fluid disposedwithin the hollow interior channel, wherein the fluid is in operativecommunication with an active material whereby the fluid effectivelyundergoes a change in at least one attribute in response to anactivation signal, wherein the change in the at least one attributechanges a shape of the seal body; an activation device in operativecommunication with the active material adapted to provide the activationsignal; and a controller in operative communication with the activationdevice.

In still another embodiment, the active seal assembly comprises a sealbody; a movable element disposed to slide within the seal body, whereinthe movable element comprises an active material adapted to selectivelymove the element from a first position to a second position in responseto an activation signal and change a shape of the seal body; anactivation device in operative communication with the active materialadapted to provide the activation signal; and a controller in operativecommunication with the activation device.

The above described and other features are exemplified by the followingfigures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are exemplary embodiments andwherein like elements are numbered alike:

FIGS. 1 and 2 illustrate contracted and expanded lengthwise sectionalviews, respectively, of a discrete active seal assembly in accordancewith one embodiment;

FIGS. 3 and 4 illustrate contracted and expanded end-on sectional views,respectively, of a discrete active seal assembly in accordance withanother embodiment;

FIGS. 5 and 6 illustrate expanded and contracted lengthwise sectionalviews, respectively, of a discrete active seal assembly in accordancewith another embodiment;

FIG. 7 illustrates a cross sectional view of an active seal assembly inaccordance with another embodiment;

FIG. 8 illustrates a cross sectional view of an active seal assembly inaccordance with another embodiment;

FIGS. 9-13 illustrate various cross sectional views of active sealassembly employing fluids that selectively expand upon actuation of anactive material; and

FIGS. 14 and 15 illustrate a cross sectional views of an active sealassembly employing movable elements in accordance with anotherembodiment.

DETAILED DESCRIPTION

Disclosed herein are discrete active sealing assemblies and methods ofuse, wherein the diameter, shape, orientation, and/or volume of thediscrete active seal assemblies can be adjusted by external means. Fordoor applications, the discrete active seal assemblies can be programmedto vary, decrease, or increase the seal force, the seal effectivenessfor the prevention or mitigation of noise, water or the like through theseal, and the ease with which entry or egress is accomplished by thevehicle operator or occupant. Although reference will be made herein toautomotive applications, it is contemplated that the active seals can beemployed for sealing opposing surfaces for various interfaces betweenopposing surfaces such as refrigerator doors, windows, drawers, and thelike. For automotive applications, the active sealing assemblies arepreferably utilized between an opening in a vehicle and a surface insliding or sealing engagement with the opening such as a vehicle door.

The discrete active sealing assemblies generally comprise an activematerial based actuator that can be selectively activated to manipulatethe properties of the seal body structure. The term “active material” asused herein refers to several different classes of materials all ofwhich exhibit a change in at least one attribute such as dimension,shape, orientation and/or elastic modulus when subjected to at least oneof many different types of applied activation signals, examples of suchsignals being thermal, electrical, magnetic, stress, and the like. Oneclass of active materials is shape memory materials. These exhibit ashape memory. Specifically, after being deformed pseudoplastically, theycan be restored to their original shape by the application of theappropriate field. In this manner, shape memory materials can change toa determined shape in response to an activation signal. Suitable shapememory materials include, without limitation, shape memory alloys (SMA),ferromagnetic SMAs (FSMA), and shape memory polymers (SMP). A secondclass of active materials can be considered as those that exhibit achange in at least one attribute when subjected to an applied field butrevert back to their original state upon removal of the applied field.Active materials in this category include, but are not limited to,piezoelectric materials, electroactive polymers (EAP), two-way trainedshape memory alloys, magnetorheological fluids and elastomers (MR),electrorheological fluids (ER), composites of one or more of theforegoing materials with non-active materials, combinations comprisingat least one of the foregoing materials, and the like. Of the abovenoted materials, SMA and SMP based discrete active seal assembliespreferably include a return mechanism to restore the original geometryof the sealing assembly. The return mechanism can be mechanical,pneumatic, hydraulic, pyrotechnic, or based on one of the aforementionedsmart materials.

During operation, the shape memory material can be configured to providean enhancement to a closure mechanism or be configured to function as amechanical closure in addition to providing selective and controlledsealing engagement. By utilizing the shape memory material in thediscrete active seal assembly, the seal assembly can change its targetedproperty to provide improved sealing engagement between opposingsurfaces, provide minimal effort to door opening and closing, as well asprovide a closure mechanism, where desired and configured. Applying anactivation signal to the shape memory material can effect the change.The return mechanism forces the active material and in operativecommunication the seal assembly to change to its original shape,orientation, elastic modulus, and/or the property effected by theactuation signal.

Optionally, the sealing structure may include one or more sensors thatare used in combination with enhanced control logic to, for example,maintain the same level of sealing force independent of aging effect andenvironmental conditions, e.g., humidity, temperature, pressuredifferential between interior and environment, and the like.

As will be discussed in greater detail below, the shape memory materialsare configured to externally actively control the seal structure, e.g.,provide actuator means, provide an exoskeleton of the seal structure;and/or can be configured to internally actively control the sealstructure, e.g., provide the skeletal structure of the seal structure.In the various embodiments disclosed herein, the seal body can generallybe formed of various rubbers, foams, elastomers, and the like, which canbe utilized in combination with the shape memory material to provide thediscrete active sealing assembly. As such, suitable seal body materialsinclude, but are not intended to be limited to, styrene butadienerubber, polyurethanes, polyisoprene, neoprene, chlorosulfonatedpolystyrenes, and the like.

In one embodiment, the discrete active seal assembly is configured suchthat the external diameter, shape, orientation, or volume of a seal bodychanges as a result of a pulling or pushing action caused by a smartmaterial actuator internally or externally disposed with the seal body.In this manner, the force with which the seal is made can be selectivelyvaried over the area that the seal occurs. This is especiallyadvantageous for door applications since vehicle door closing andopening efforts can be reduced. Vehicle doors typically include apassive seal body peripherally disposed about the door and adapted tocompress upon contact with a doorframe to seal the gap between these twovehicle parts. By selectively varying the shape of the seal body alongthe perimeter of the door, seal force and/or area can be activelymanipulated and the seal effectiveness can be altered.

In one embodiment, the force is varied by transferring the force from anactive material based actuator through the geometry of the seal body.The active material based actuator can directly transmit the necessaryforce to do this by mechanical changes of the seal body or indirectly,such as by use of a fluid within the seal body that selectively fillsand empties, or expands and contracts, or by other means of transmittingthe force to where it is required. The fluid can be configured toprovide selective filling and emptying by being in direct communicationwith the active material based actuator, or alternatively, the fluid canbe in selective communication with a pressurized reservoir andselectively pressurized by means of an active material based valveand/or selectively depressurized by means of another active materialbased release valve. One of the many advantages that result from the useof the shape memory materials is the elimination of bulky, andcomplicated motors; which reduces the number of possible failure modesassociated with this conventional approach.

Turning now to FIG. 1, an exemplary discrete active seal assembly shownin lateral cross section (i.e. a cross section along the length of theseal), generally indicated by reference numeral 10, is shown. The sealassembly 10 includes a seal body 12 with stiffening elements 14 attachedto a spine 16 within the seal body 12. Each stiffening element 14includes one pivotable end attached to the spine 16 and the other endattached to an inner surface of the seal body 12. The spine 16 ismechanically connected to an active material based actuator 18, whereinthe active material provides a displacement to effect movement of thespine 16 along the length of the seal. It is this movement that causesthe stiffening elements 14 to transmit a force along the length of theseal to change the shape of the seal (and hence some degree of forceenhancement or reduction) as shown in FIG. 2. The active material basedactuator can be any one of the aforementioned materials adapted toprovide a suitable amount of displacement to the spine. For example, theactive material based actuator can be a spring formed of a shape memoryalloy, a piezoelectric unimorph or bimorph, a piezoelectric inchworm, aferromagnetic shape memory actuator and the like. As is well known andappreciated by those in the art, the aforementioned active materials andconsequently active materials based actuators, have the ability torecover strain in response to a suitable activation signal. For example,shape memory alloys can change from a deformed shape to a previously“memorized” shape when heated. Likewise, piezoelectrics produce amechanical deformation in response to an applied charge.

Other suitable shearing designs will be apparent to those skilled in theart in view of this disclosure. Force is applied at an end of the sealstructure and the herringbone-like structure of the stiffening elementsand spine (FIG. 1) is translated into vertical motion (FIG. 2) of theseal body enabling enhanced sealing.

As noted above, the active material or active material based actuatorcan be employed to provide the displacement required to change thegeometry of the seal body. An activation device (not shown) is inoperative communication with the active material or active materialbased actuator and a controller (not shown) for selectively providingthe activation signal. The active material or active material basedactuator provides a force effective to provide the desired amount ofdisplacement or alternatively, may be used to form the stiffeningelements such that activation of the active material or active materialbased actuator changes its shape orientation to effect the verticaldisplacement. Preferably, continuously controllable active materials oractive material based actuators are employed in this embodiment, e.g.,dielectric elastomers, magnetic shape memory alloys, bimorphpiezoceramics or piezopolymers, IPMCs, and the like. Other designsinclude deformation or buckling of the internal structure of the seal,auxetic-type internal geometries, and so forth.

In some embodiments, it may be desirable to have the overall motion ofthe outer portion of the seal be in the sealing force direction sinceshearing or motion at angles to this direction may cause a gap in theseal at one end, or introduce a constraint on the seal that involvesshearing stresses perpendicular to the sealing force direction whichmight slip during vehicle motion. As such, it may be preferred to applyforce at both ends of the seal assembly. For example, the top surfaceand mid plane of the seal assembly may preferably be made with a rigidinternal structure (such as a steel strip or a set of wires) that willconstrain the top surface of the seal at one end, and allow relativedisplacement of the mid plane to propagate along the length of the seal.

In another embodiment as shown in longitudinal cross section (i.e. across section perpendicular to the length of the seal) in FIGS. 3 and 4,an exemplary discrete active seal assembly 20 is illustrated with atwisting design. A shape memory material 22, e.g., wires formed of ashape memory alloy, is formed into a spoke like arrangement about acentral axis (e.g., spine) 24 within a seal body 26. Upon activation,the spokes 22 would change its shape from the relative straight shapeorientation shown in FIG. 3 to the contracted shape shown in FIG. 4thereby resulting in a contraction of the seal assembly 20.Discontinuing the activation signal would cause the original shape toreturn. Of course, the shape memory material and geometry of the sealassembly 20 can be selected so as to provide expansion upon activation,if desired. For shape memory alloys and shape memory polymers, dependingon the configuration it may be desirable to utilize a biasing element torestore the original spoke geometry.

Optionally, collapse of the seal body 26 as shown in FIG. 4 may beaccomplished through torsion about the central axis 24. In thisembodiment, spokes 22 are elastic wires, vanes, or strips in mechanicalcommunication with the exterior seal body 26. Through torsion about thecentral axis 24, the spokes 22 are deformed radially, causing theexternal surface to collapse inward. In this embodiment, the centralspoke 24 is in mechanical communication with a torsion type activematerial or active material based actuator, not shown. Suitable activematerials or active material based actuators include shape memory alloywires, torque tubes, or actuators, rotary dielectric elastomeractuators, piezoelectric bimorph actuators, and the like.

In another embodiment, the discrete active seal assemblies are adaptedto provide a pushing or pulling action. Deformation of the seal body inthese embodiments is generally accomplished by transmitting a force ofthe active material or active material based actuator to an end of theseal structure into a vertical bending or twisting motion. As shown inthe longitudinal cross section provided in FIGS. 5 and 6, an exemplarydiscrete active sealing assembly 30 includes a plurality of elasticfinger-like projections 32 that include a wire 34 extending therein. Aportion of the wire is disposed axisymetrically along the length of thefinger-like projection with an end of the wire fixedly attached to thefinger-like projection at position distally located from a base of theseal body. Collectively, the wires 34 are mechanically operative with apulley 36, which is terminally connected to an active material or activematerial based actuator 38. The active material or active material basedactuator 38 selectively exerts a pulling force on the wires 34 inresponse to an activation signal to the active material causing thefinger-like projections 32 to bend. Optionally, a low-friction orfrictionless channel is employed in place of the pulleys 36.

FIG. 7 illustrates a cross-section of an alternative discrete activeseal assembly 40 of the push/pull type that includes a flexible rigidelement 42 embedded within a seal body 46. A wire or the like isattached to element 42 at an end distally located from the base 48 ofthe seal body 46. The other end of the wire is attached to an activematerial or active material based actuator. Upon activation of theactive material or active material based actuator, a force is exerted onthe rigid element to cause bending of the seal body. A suitable flexiblerigid element can be a thin strip formed of plastic or a metal such assteel. The rigid element 42 can be configured to provide a biasing forcein the absence of the activation signal, thereby restoring the seal bodyto its original position.

FIG. 8 illustrates yet another variation of a push/pull discrete activeseal assembly in longitudinal cross section. In this illustrated sealassembly 50, the seal body 52 has a three compressible chambers 54extending along its length. It should be noted that more or lesschambers could be employed depending on the desired application. Wiresor strips 56 are embedded within the seal body 52 in a position betweenthe chambers. By exerting a pulling force on the wires 56 with anactuator 58, compression of the seal body 52 can be made to selectivelyoccur.

As an alternate variation of FIG. 8, a continuous seal assembly can beformed by replacing the wires or strips 56 with active material basedbending elements such as piezoelectric bimorphs, shape memory alloybimorphs, IPMCs and the like.

In the embodiments shown in FIGS. 5-8, it should be apparent to those inthe art that the degree of deflection of the seal body can be readilycontrolled by the location of the wires and the amount of actuationprovided by the active material or active material based actuator.

FIG. 9 illustrates a lateral cross section of a discrete active sealassembly 60 that employs a fluid pressure change to alter the seal forceof a seal body. In this embodiment, the fluid pressure is changedthrough the use of an active material or active material based actuator.The discrete active seal assembly 60 includes a seal body 62 having achamber 64 in fluid communication with a reservoir 66. The reservoir 66can be filled with a suitable pressurizing fluid or gas. In oneembodiment, the fluid reservoir is pressurized using conventional means.In another embodiment, the fluid reservoir is pressurized using anactive material or active material based actuator. Means are provided ineither embodiment for on-demand forcible transfer of fluid into or outof the seal structure. In this manner, the seal body may be eitherexpanded (to force a more intimate seal with between adjacent structuralsurfaces) or contracted (to reduce the sealing force).

The fluid reservoir 66 can take many forms. For example, it can beconfigured as an explicit pump, e.g., standard compressors, impellers,accumulators, and the like. It can also be configured using pumps basedon active materials such as shape memory alloys, piezoelectric ceramics,dielectric elastomers, and the like. In such a design, fluid would beexplicitly moved into and out of the seal upon demand using a compactfluid pump. The reservoir 66 can also be single-stroke in design. Forinstance, the fluid reservoir could be a flexible structure actuatedusing linear contractile elements such as shape memory alloy wires,liquid crystal elastomers, conductive polymers, electroactive polymergels, and the like, or expansion type elements such as dielectricelastomers, piezoelectric polymers, and so forth. Alternatively, anouter covering of the fluid reservoir 66 can comprise the activematerial, e.g., a shape memory alloy or polymer.

The combined structure of the active material and passive elasticmaterial of the seal body 62 is disposed suitably so as to forciblyincrease or decrease the volume available to be occupied by the fluid.The biased fluid reservoir 66 is considered to be connected with theseal body in such a way that fluid can transmit between the twostructures; the structure of the fluid reservoir is arranged such that,in the absence of resistance, fluid is expelled from the reservoir. Whenplaced in fluid communication, and upon activating the active material,the seal assembly 60 would either allow fluid into the seal body 62 fromthe biased fluid reservoir 66, or force fluid out of the seal body 62and into the biased fluid reservoir 66. This configuration preferablyutilizes shape memory materials that are used in a one-way mode, or needto be “reset”. An active valve 68 between the two components (seal body62 and fluid reservoir 64) may also be a component of this embodiment.

In another embodiment the seal assembly 60 can be adapted to transfer orharvest energy associated with any part of entry/egress to modifying thesealing force or geometry. For example, as shown in lateral crosssection in FIG. 10, the energy associated with the rising/sitting of thepassenger from a seat assembly 70 can be used to power a small pump topressurize the fluid reservoir 66 (can be viscous, i.e., slow actingthrough a throttle valve, for instance, so as to be transparent withregards to the effort with which this occurs; displacement could also besmall if a large area beneath the seat were employed). Alternatively,energy could also be harvested from the periodic motion associated withthe coupled spring-mass system of the driver/passenger and seat assembly72 via a peristaltic or a force-rectified pump assembly, and stored in apressurized fluid reservoir 66. The pump 74 would then either directlyapply and/or release pressure into some portion of the seal, or act as apressurized reservoir for transduction of that force into theappropriate kind of energy for activation and/or deactivation of theactive-material based actuator. In the embodiment shown, the energycould be captured in electrical form and transferred. For example,charging a capacitor or battery from the captured energy of relativepassenger and vehicle motion. Alternatively, pistons 72 upon which theseat assembly is mounted can be employed to forcibly push the fluid toraise the seat.

FIG. 11 illustrates an exemplary cross section of a fluid based sealassembly 80 that can be employed to minimize the amount of fluid used tochange the sealing force. The seal assembly 80 includes an outerresilient contact surface 82 and inner hard core 84 that collectivelydefine an inner fluid passageway 86. By selecting a material for theinner hard core to be relatively rigid, upon activation of fluid withinthe fluid passageway causes outward expansion of the outer resilientcontact surface 82 relative to the inner core 84.

FIGS. 12 and 13 illustrate longitudinal cross sections of a fluid basedactive seal assembly 90 that includes a fluid channel 96 disposedbetween two inner hard cores 94 extending along the length of the sealbody 92. A portion 98 of the fluid channel 96 extends beyond the twoinner core materials such that upon fluid expansion, the portion 98expands and exerts a force on the seal force to cause expansion thereof(as shown more clearly in FIG. 13). Other cross sectional designs thatprovide increased seal effectiveness and minimal fluid will be apparentto those in the art in view of this disclosure.

FIGS. 14 and 15 illustrates a discrete active seal assembly thataugments the seal force of the seal body. In this embodiment, thediscrete active seal assembly includes a movable element disposed withinthe seal body such that movement of the movable element from a firstlocation to a second location within the seal body provides a volumeincrease in the region of the seal body corresponding to the secondlocation. At the same time, a reduction in volume can occur in the firstlocation. The mechanism for moving the movable element can be actuatedby an active material based actuator or may be mechanically actuated.For example, for mechanical actuation, the movement of a vehicle windowinto the seal body could be used to move the movable element andincrease the seal volume as a result of that movement, therebyincreasing seal force.

As shown, the discrete active seal assembly 100 includes a slidingmovable element 102 disposed within a seal body 104. The seal body isformed of a flexible elastic material and includes a channel 103dimensioned to elastically expand so as to accommodate the movableelement as it transitions from a first position 106 to a second position(shown by dotted line arrow 108). Upon movement of the movable element102 from the first position 106 to the second position 108, the sealbody 104 will outwardly expand to accommodate the movable element 106,thereby providing an increase in seal force.

In another embodiment, the discrete active seal assembly 120 furtherincludes a spring 122 formed of a shape memory alloy for moving themovable element 102 to the second position 108 and a bias spring 124 forreturning the movable element 102 to the first position 106.

As previously discussed, the term “active material” refers to severaldifferent classes of materials all of which exhibit a change in at leastone attribute such as dimension, shape, and/or flexural modulus whensubjected to at least one of many different types of applied activationsignals, examples of such signals being thermal, electrical, magnetic,stress, and the like. One class of active materials is shape memorymaterials. These exhibit a shape memory. Specifically, after beingdeformed pseudoplastically, they can be restored to their original shapeby the application of the appropriate field. In this manner, shapememory materials can change to a determined shape in response to anactivation signal. Suitable shape memory materials include, withoutlimitation, shape memory alloys (SMA), ferromagnetic SMAs (FSMA), andshape memory polymers (SMP). A second class of active materials can beconsidered as those that exhibit a change in at least one attributedescribed above when subjected to an applied field but revert back totheir original state upon removal of the applied field. Active materialsin this category include, but are not limited to, piezoelectricmaterials, electroactive polymers (EAP), two-way trained shape memoryalloys, magnetorheological fluids and elastomers (MR),electrorheological fluids (ER), composites of one or more of theforegoing materials with non-active materials, combinations comprisingat least one of the foregoing materials, and the like. Depending on theparticular active material, the activation signal can take the form of,without limitation, an electric current, a temperature change, amagnetic field, a mechanical loading or stressing, or the like. Of theabove noted materials, SMA and SMP based discrete active seal assembliespreferably include a return mechanism to restore the original geometryof the sealing assembly. The return mechanism can be mechanical,pneumatic, hydraulic, pyrotechnic, or based on one of the aforementionedsmart materials.

Suitable piezoelectric materials include, but are not intended to belimited to, inorganic compounds, organic compounds, and metal oxides.With regard to organic materials, all of the polymeric materials withnon-centrosymmetric structure and large dipole moment group(s) on themain chain or on the side-chain, or on both chains within the molecules,can be used as suitable candidates for the piezoelectric film. Exemplarypolymers include, for example, but are not limited to, poly(sodium4-styrenesulfonate), poly (poly(vinylamine)backbone azo chromophore),and their derivatives; polyfluorocarbons, includingpolyvinylidenefluoride, its co-polymer vinylidene fluoride (“VDF”),co-trifluoroethylene, and their derivatives; polychlorocarbons,including poly(vinyl chloride), polyvinylidene chloride, and theirderivatives; polyacrylonitriles, and their derivatives; polycarboxylicacids, including poly(methacrylic acid), and their derivatives;polyureas, and their derivatives; polyurethanes, and their derivatives;bio-molecules such as poly-L-lactic acids and their derivatives, andcell membrane proteins, as well as phosphate bio-molecules such asphosphodilipids; polyanilines and their derivatives, and all of thederivatives of tetramines; polyamides including aromatic polyamides andpolyimides, including Kapton and polyetherimide, and their derivatives;all of the membrane polymers; poly(N-vinyl pyrrolidone) (PVP)homopolymer, and its derivatives, and random PVP-co-vinyl acetatecopolymers; and all of the aromatic polymers with dipole moment groupsin the main-chain or side-chains, or in both the main-chain and theside-chains, and mixtures thereof.

Piezoelectric material can also comprise metal oxides selected from thegroup consisting of lead, antimony, manganese, tantalum, zirconium,niobium, lanthanum, platinum, palladium, nickel, tungsten, aluminum,strontium, titanium, barium, calcium, chromium, silver, iron, silicon,copper, alloys comprising at least one of the foregoing metals, andoxides comprising at least one of the foregoing metals. Suitable metaloxides include SiO₂, Al₂O₃, ZrO₂, TiO₂, SrTiO₃, PbTiO₃, BaTiO₃, Fe0₃,Fe₃0₄, ZnO, and mixtures thereof and Group VIA and IIB compounds, suchas CdSe, CdS, GaAs, AgCaSe₂, ZnSe, GaP, InP, ZnS, and mixtures thereof.Preferably, the piezoelectric material is selected from the groupconsisting of polyvinylidene fluoride, lead zirconate titanate, andbarium titanate, and mixtures thereof.

Shape memory polymers (SMPs) generally refer to a group of polymericmaterials that demonstrate the ability to return to some previouslydefined shape when subjected to an appropriate thermal stimulus. Theshape memory polymer may be in the form of a solid or a foam as may bedesired for some embodiments. Shape memory polymers are capable ofundergoing phase transitions in which their shape orientation is alteredas a function of temperature. Generally, SMPs are co-polymers comprisedof at least two different units which may be described as definingdifferent segments within the copolymer, each segment contributingdifferently to the flexural modulus properties and thermal transitiontemperatures of the material. The term “segment” refers to a block,graft, or sequence of the same or similar monomer or oligomer units thatare copolymerized with a different segment to form a continuouscrosslinked interpenetrating network of these segments. These segmentsmay be combination of crystalline or amorphous materials and thereforemay be generally classified as a hard segment(s) or a soft segment(s),wherein the hard segment generally has a higher glass transitiontemperature (Tg) or melting point than the soft segment. Each segmentthen contributes to the overall flexural modulus properties of the SMPand the thermal transitions thereof. When multiple segments are used,multiple thermal transition temperatures may be observed, wherein thethermal transition temperatures of the copolymer may be approximated asweighted averages of the thermal transition temperatures of itscomprising segments. With regard to shape memory polymer foams, thestructure may be open celled or close celled as desired.

In practice, the SMPs are alternated between one of at least two shapeorientations such that at least one orientation will provide a sizereduction relative to the other orientation(s) when an appropriatethermal signal is provided. To set a permanent shape, the shape memorypolymer must be at about or above its melting point or highesttransition temperature (also termed “last” transition temperature). SMPfoams are shaped at this temperature by blow molding or shaped with anapplied force followed by cooling to set the permanent shape. Thetemperature necessary to set the permanent shape is generally betweenabout 40° C. to about 200° C. After expansion by fluid, the permanentshape is regained when the applied force is removed, and the expandedSMP is again brought to or above the highest or last transitiontemperature of the SMP. The Tg of the SMP can be chosen for a particularapplication by modifying the structure and composition of the polymer.

The temperature needed for permanent shape recovery can generally be setat any temperature between about −63° C. and about 160° C. or above.Engineering the composition and structure of the polymer itself canallow for the choice of a particular temperature for a desiredapplication. A preferred temperature for shape recovery is greater thanor equal to about −30° C., more preferably greater than or equal toabout 20° C., and most preferably a temperature greater than or equal toabout 70° C. Also, a preferred temperature for shape recovery is lessthan or equal to about 250° C., more preferably less than or equal toabout 200° C., and most preferably less than or equal to about 180° C.

Suitable shape memory polymers can be thermoplastics, interpenetratingnetworks, semi-interpenetrating networks, or mixed networks. Thepolymers can be a single polymer or a blend of polymers. The polymerscan be linear or branched thermoplastic elastomers with side chains ordendritic structural elements. Suitable polymer components to form ashape memory polymer include, but are not limited to, polyphosphazenes,poly(vinyl alcohols), polyamides, polyester amides, poly(amino acids),polyanhydrides, polycarbonates, polyacrylates, polyalkylenes,polyacrylamides, polyalkylene glycols, polyalkylene oxides, polyalkyleneterephthalates, polyortho esters, polyvinyl ethers, polyvinyl esters,polyvinyl halides, polyesters, polylactides, polyglycolides,polysiloxanes, polyurethanes, polyethers, polyether amides, polyetheresters, and copolymers thereof. Examples of suitable polyacrylatesinclude poly(methyl methaciylate), poly(ethyl methacrylate), poly(butylmethacrylate), poly(isobutyl methacrylate), poly(hexyl methacrylate),poly(isodecyl methacrylate), poly(lauryl methacrylate), poly(phenylmethacrylate), poly(methyl acrylate), poly(isopropyl acrylate),poly(isobutyl acrylate) and poly(octadecylacrylate). Examples of othersuitable polymers include polystyrene, polypropylene, polyvinyl phenol,polyvinylpyrrolidone, chlorinated polybutylene, poly(octadecyl vinylether), ethylene vinyl acetate, polyethylene, poly(ethyleneoxide)-poly(ethylene terephthalate), polyethylene/nylon (graftcopolymer), polycaprolactones-polyamide (block copolymer),poly(caprolactone) diniethacrylate-n-butyl acrylate,poly(norbornyl-polyhedral oligomeric silsequioxane), polyvinylchloride,urethane/butadiene copolymers, polyurethane block copolymers,styrene-butadienestyrene block copolymers, and the like.

Conducting polymerization of different monomer segments with a blowingagent can be used to form the shape memory polymer foam, if desired. Theblowing agent can be of the decomposition type (evolves a gas uponchemical decomposition) or an evaporation type (which vaporizes withoutchemical reaction). Exemplary blowing agents of the decomposition typeinclude, but are not intended to be limited to, sodium bicarbonate,azide compounds, ammonium carbonate, ammonium nitrite, light metalswhich evolve hydrogen upon reaction with water, azodicarbonamide,N,N′dinitrosopentamethylenetetramine, and the like. Exemplary blowingagents of the evaporation type include, but are not intended to belimited to, trichloromonofluoromethane, trichlorotrifluoroethane,methylene chloride, compressed nitrogen gas, and the like. The materialcan then be reverted to the permanent shape by heating the materialabove its Tg but below the highest thermal transition temperature ormelting point. Thus, by combining multiple soft segments it is possibleto demonstrate multiple temporary shapes and with multiple hard segmentsit may be possible to demonstrate multiple permanent shapes.

As previously discussed, other suitable shape memory materials alsoinclude shape memory alloy compositions. Shape memory alloys exist inseveral different temperature-dependent phases. The most commonlyutilized of these phases are the so-called martensite and austenitephases. In the following discussion, the martensite phase generallyrefers to the more deformable, lower temperature phase whereas theaustenite phase generally refers to the more rigid, higher temperaturephase. When the shape memory alloy is in the martensite phase and isheated, it begins to change into the austenite phase. The temperature atwhich this phenomenon starts is often referred to as austenite starttemperature (As). The temperature at which this phenomenon is completeis called the austenite finish temperature (Af). When the shape memoryalloy is in the austenite phase and is cooled, it begins to change intothe martensite phase, and the temperature at which this phenomenonstarts is referred to as the martensite start temperature (Ms). Thetemperature at which austenite finishes transforming to martensite iscalled the martensite finish temperature (Mf). Generally, the shapememory alloys are softer and more easily deformable in their martensiticphase and are harder, stiffer, and/or more rigid in the austeniticphase. In view of the foregoing properties, expansion of the shapememory alloy is preferably at or below the austenite transitiontemperature (at or below As). Subsequent heating above the austenitetransition temperature causes the expanded shape memory alloy to revertback to its permanent shape. Thus, a suitable activation signal for usewith shape memory alloys is a thermal activation signal having amagnitude to cause transformations between the martensite and austenitephases.

The temperature at which the shape memory alloy remembers its hightemperature form when heated can be adjusted by slight changes in thecomposition of the alloy and through heat treatment. In nickel-titaniumshape memory alloys, for instance, it can be changed from above about100° C. to below about −100° C. The shape recovery process occurs over arange of just a few degrees and the start or finish of thetransformation can be controlled to within a degree or two depending onthe desired application and alloy composition. The mechanical propertiesof the shape memory alloy vary greatly over the temperature rangespanning their transformation, typically providing shape memory effects,superelastic effects, and high damping capacity.

Suitable shape memory alloy materials include, but are not intended tobe limited to, nickel-titanium based alloys, indium-titanium basedalloys, nickel-aluminum based alloys, nickel-gallium based alloys,copper based alloys (e.g., copper-zinc alloys, copper-aluminum alloys,copper-gold, and copper-tin alloys), gold-cadmium based alloys,silver-cadmium based alloys, indium-cadmium based alloys,manganese-copper based alloys, iron-platinum based alloys,iron-palladium based alloys, and the like. The alloys can be binary,ternary, or any higher order so long as the alloy composition exhibits ashape memory effect, e.g., change in shape orientation, changes in yieldstrength, and/or flexural modulus properties, damping capacity,superelasticity, and the like. A preferred shape memory alloy is anickel-titanium based alloy commercially available under the trademarkFLEXINOL from Dynalloy, Inc. Selection of a suitable shape memory alloycomposition depends on the temperature range where the component willoperate.

Suitable magnetic materials include, but are not intended to be limitedto, soft or hard magnets; hematite; magnetite; magnetic material basedon iron, nickel, and cobalt, alloys of the foregoing, or combinationscomprising at least one of the foregoing, and the like. Alloys of iron,nickel and/or cobalt, can comprise aluminum, silicon, cobalt, nickel,vanadium, molybdenum, chromium, tungsten, manganese and/or copper.

Suitable MR fluid materials include, but are not intended to be limitedto, ferromagnetic or paramagnetic particles dispersed in a carrierfluid. Suitable particles include iron; iron alloys, such as thoseincluding aluminum, silicon, cobalt, nickel, vanadium, molybdenum,chromium, tungsten, manganese and/or copper; iron oxides, includingFe₂O₃ and Fe₃O₄; iron nitride; iron carbide; carbonyl iron; nickel andalloys of nickel; cobalt and alloys of cobalt; chromium dioxide;stainless steel; silicon steel; and the like. Examples of suitableparticles include straight iron powders, reduced iron powders, ironoxide powder/straight iron powder mixtures and iron oxide powder/reducediron powder mixtures. A preferred magnetic-responsive particulate iscarbonyl iron, preferably, reduced carbonyl iron.

The particle size should be selected so that the particles exhibitmulti-domain characteristics when subjected to a magnetic field.Diameter sizes for the particles can be less than or equal to about 1000micrometers, with less than or equal to about 500 micrometers preferred,and less than or equal to about 100 micrometers more preferred. Alsopreferred is a particle diameter of greater than or equal to about 0.1micrometer, with greater than or equal to about 0.5 more preferred, andgreater than or equal to about 10 micrometers especially preferred. Theparticles are preferably present in an amount between about 5.0 to about50 percent by volume of the total MR fluid composition.

Suitable carrier fluids include organic liquids, especially non-polarorganic liquids. Examples include, but are not limited to, siliconeoils; mineral oils; paraffin oils; silicone copolymers; white oils;hydraulic oils; transformer oils; halogenated organic liquids, such aschlorinated hydrocarbons, halogenated paraffins, perfluorinatedpolyethers and fluorinated hydrocarbons; diesters; polyoxyalkylenes;fluorinated silicones; cyanoalkyl siloxanes; glycols; synthetichydrocarbon oils, including both unsaturated and saturated; andcombinations comprising at least one of the foregoing fluids.

The viscosity of the carrier component can be less than or equal toabout 100,000 centipoise, with less than or equal to about 10,000centipoise preferred, and less than or equal to about 1,000 centipoisemore preferred. Also preferred is a viscosity of greater than or equalto about 1 centipoise, with greater than or equal to about 250centipoise preferred, and greater than or equal to about 500 centipoiseespecially preferred.

Aqueous carrier fluids may also be used, especially those comprisinghydrophilic mineral clays such as bentonite or hectorite. The aqueouscarrier fluid may comprise water or water comprising a small amount ofpolar, water-miscible organic solvents such as methanol, ethanol,propanol, dimethyl sulfoxide, dimethyl formamide, ethylene carbonate,propylene carbonate, acetone, tetrahydrofuran, diethyl ether, ethyleneglycol, propylene glycol, and the like. The amount of polar organicsolvents is less than or equal to about 5.0% by volume of the total MRfluid, and preferably less than or equal to about 3.0%. Also, the amountof polar organic solvents is preferably greater than or equal to about0.1%, and more preferably greater than or equal to about 1.0% by volumeof the total MR fluid. The pH of the aqueous carrier fluid is preferablyless than or equal to about 13, and preferably less than or equal toabout 9.0. Also, the pH of the aqueous carrier fluid is greater than orequal to about 5.0, and preferably greater than or equal to about 8.0.

Natural or synthetic bentonite or hectorite may be used. The amount ofbentonite or hectorite in the MR fluid is less than or equal to about 10percent by weight of the total MR fluid, preferably less than or equalto about 8.0 percent by weight, and more preferably less than or equalto about 6.0 percent by weight. Preferably, the bentonite or hectoriteis present in greater than or equal to about 0.1 percent by weight, morepreferably greater than or equal to about 1.0 percent by weight, andespecially preferred greater than or equal to about 2.0 percent byweight of the total MR fluid.

Optional components in the M fluid include clays, organoclays,carboxylate soaps, dispersants, corrosion inhibitors, lubricants,extreme pressure anti-wear additives, antioxidants, thixotropic agentsand conventional suspension agents. Carboxylate soaps include ferrousoleate, ferrous naphthenate, ferrous stearate, aluminum di- andtri-stearate, lithium stearate, calcium stearate, zinc stearate andsodium stearate, and surfactants such as sulfonates, phosphate esters,stearic acid, glycerol monooleate, sorbitan sesquioleate, laurates,fatty acids, fatty alcohols, fluoroaliphatic polymeric esters, andtitanate, aluminate and zirconate coupling agents and the like.Polyalkylene diols, such as polyethylene glycol, and partiallyesterified polyols can also be included.

Suitable MR elastomer materials include, but are not intended to belimited to, an elastic polymer matrix comprising a suspension offerromagnetic or paramagnetic particles, wherein the particles aredescribed above. Suitable polymer matrices include, but are not limitedto, poly-alpha-olefins, natural rubber, silicone, polybutadiene,polyethylene, polyisoprene, and the like.

Electroactive polymers include those polymeric materials that exhibitpiezoelectric, pyroelectric, or electrostrictive properties in responseto electrical or mechanical fields. An example of anelectrostrictive-grafted elastomer with a piezoelectric poly(vinylidenefluoride-trifluoro-ethylene) copolymer. This combination has the abilityto produce a varied amount of ferroelectric-electrostrictive molecularcomposite systems. These may be operated as a piezoelectric sensor oreven an electrostrictive actuator.

Materials suitable for use as an electroactive polymer may include anysubstantially insulating polymer or rubber (or combination thereof) thatdeforms in response to an electrostatic force or whose deformationresults in a change in electric field. Exemplary materials suitable foruse as a pre-strained polymer include silicone elastomers, acrylicelastomers, polyurethanes, thermoplastic elastomers, copolymerscomprising PVDF, pressure-sensitive adhesives, fluoroelastomers,polymers comprising silicone and acrylic moieties, and the like.Polymers comprising silicone and acrylic moieties may include copolymerscomprising silicone and acrylic moieties, polymer blends comprising asilicone elastomer and an acrylic elastomer, for example.

Materials used as an electroactive polymer may be selected based on oneor more material properties such as a high electrical breakdownstrength, a low modulus of elasticity—(for large or small deformations),a high dielectric constant, and the like. In one embodiment, the polymeris selected such that is has an elastic modulus at most about 100 MPa.In another embodiment, the polymer is selected such that is has amaximum actuation pressure between about 0.05 MPa and about 10 MPa, andpreferably between about 0.3 MPa and about 3 MPa. In another embodiment,the polymer is selected such that is has a dielectric constant betweenabout 2 and about 20, and preferably between about 2.5 and about 12. Thepresent disclosure is not intended to be limited to these ranges.Ideally, materials with a higher dielectric constant than the rangesgiven above would be desirable if the materials had both a highdielectric constant and a high dielectric strength. In many cases,electroactive polymers may be fabricated and implemented as thin films.Thicknesses suitable for these thin films may be below 50 micrometers.

As electroactive polymers of the present invention may deflect at highstrains, electrodes attached to the polymers should also deflect withoutcompromising mechanical or electrical performance. Generally, electrodessuitable for use may be of any shape and material provided that they areable to supply a suitable voltage to, or receive a suitable voltagefrom, an electroactive polymer. The voltage may be either constant orvarying over time. In one embodiment, the electrodes adhere to a surfaceof the polymer. Electrodes adhering to the polymer are preferablycompliant and conform to the changing shape of the polymer.Correspondingly, the present disclosure may include compliant electrodesthat conform to the shape of an electroactive polymer to which they areattached. The electrodes may be only applied to a portion of anelectroactive polymer and define an active area according to theirgeometry. Various types of electrodes suitable for use with the presentdisclosure include structured electrodes comprising metal traces andcharge distribution layers, textured electrodes comprising varying outof plane dimensions, conductive greases such as carbon greases or silvergreases, colloidal suspensions, high aspect ratio conductive materialssuch as carbon fibrils and carbon nanotubes, and mixtures of ionicallyconductive materials.

Materials used for electrodes of the present invention may vary.Suitable materials used in an electrode may include graphite, carbonblack, colloidal suspensions, thin metals including silver and gold,silver filled and carbon filled gels and polymers, and ionically orelectronically conductive polymers. It is understood that certainelectrode materials may work well with particular polymers and may notwork as well for others. By way of example, carbon fibrils work wellwith acrylic elastomer polymers while not as well with siliconepolymers.

While the disclosure has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof. Therefore, it is intended that thedisclosure not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this disclosure, but that thedisclosure will include all embodiments falling within the scope of theappended claims.

1. An active seal assembly, comprising: a seal body formed of an elasticmaterial integrated with a seal base, wherein the seal bodylongitudinally defines a hollow interior channel and interior surface; awire or strip predominately disposed within the hollow interior channelcomprising a plurality of stiff elements fixedly attached to theinterior surface and disposed within the channel; an active material inoperative communication with and drivenly coupled to the end of the wireor strip, wherein the active material is effective to undergo a changein at least one attribute in response to an activation signal, whereinthe change in the at least one attribute exerts a force on the wire orstrip operable to change a shape of the seal body; an activation devicein operative communication with the active material adapted to providethe activation signal; and a controller in operative communication withthe activation device.
 2. The active seal assembly of claim 1, whereinthe wire or strip rotates in response to the activation signal todecrease a cross sectional diameter of the seal body.
 3. The active sealassembly of claim 1, wherein the active material is selected from thegroup consisting of shape memory alloys, ferromagnetic shape memoryalloys, shape memory polymers, electroactive polymers,magnetorheological elastomers and piezoelectric materials.
 4. The activeseal assembly of claim 1, wherein the stiffening elements are formed ofthe active material.
 5. The active seal assembly of claim 1, wherein thewire or strip is centrally disposed within the hollow interior channel.